Math Problem Statement

verify that the equation is an identity: csc(x)-sin(x)=(cos(x))(cot(x))

Solution

To verify that the equation

csc(x)sin(x)=cos(x)cot(x)\csc(x) - \sin(x) = \cos(x) \cdot \cot(x)

is an identity, let's work through both sides and check if they are equivalent.

Step 1: Rewrite Both Sides Using Trigonometric Identities

  1. Left Side: csc(x)sin(x)\csc(x) - \sin(x)

    Recall that:

    • csc(x)=1sin(x)\csc(x) = \frac{1}{\sin(x)}

    Substituting, we get: csc(x)sin(x)=1sin(x)sin(x)\csc(x) - \sin(x) = \frac{1}{\sin(x)} - \sin(x)

    We can combine terms by expressing sin(x)\sin(x) as sin2(x)sin(x)\frac{\sin^2(x)}{\sin(x)}: 1sin(x)sin(x)=1sin2(x)sin(x)\frac{1}{\sin(x)} - \sin(x) = \frac{1 - \sin^2(x)}{\sin(x)}

    Next, use the Pythagorean identity 1sin2(x)=cos2(x)1 - \sin^2(x) = \cos^2(x): 1sin2(x)sin(x)=cos2(x)sin(x)\frac{1 - \sin^2(x)}{\sin(x)} = \frac{\cos^2(x)}{\sin(x)}

    So, the left side simplifies to: cos2(x)sin(x)\frac{\cos^2(x)}{\sin(x)}

  2. Right Side: cos(x)cot(x)\cos(x) \cdot \cot(x)

    Recall that:

    • cot(x)=cos(x)sin(x)\cot(x) = \frac{\cos(x)}{\sin(x)}

    Substituting, we get: cos(x)cot(x)=cos(x)cos(x)sin(x)=cos2(x)sin(x)\cos(x) \cdot \cot(x) = \cos(x) \cdot \frac{\cos(x)}{\sin(x)} = \frac{\cos^2(x)}{\sin(x)}

Conclusion

Both the left side and right side simplify to cos2(x)sin(x)\frac{\cos^2(x)}{\sin(x)}, so:

csc(x)sin(x)=cos(x)cot(x)\csc(x) - \sin(x) = \cos(x) \cdot \cot(x)

Thus, the equation is indeed an identity.

Would you like further details on any part of this solution?


Here are five related questions to consider:

  1. What are some other common trigonometric identities?
  2. How do you simplify expressions involving csc(x)\csc(x) or cot(x)\cot(x)?
  3. Can this identity be derived using other trigonometric identities?
  4. Why is the Pythagorean identity useful in simplifying trigonometric expressions?
  5. How would you verify a trigonometric identity if both sides have multiple trigonometric functions?

Tip: When verifying trigonometric identities, try to express everything in terms of sin(x)\sin(x) and cos(x)\cos(x) — this often simplifies the process!

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Trigonometric Identities

Formulas

csc(x) = 1/sin(x)
cot(x) = cos(x)/sin(x)
Pythagorean identity: sin^2(x) + cos^2(x) = 1

Theorems

Pythagorean Identity

Suitable Grade Level

Grades 10-12